A gas meter is known that has a wheel rotating about an axis relative to a structure in such a manner that the speed of rotation of the wheel is representative of the quantity of gas distributed.
The gas meter has a device for counting the number of revolutions of the wheel. The counter device comprises a target, a target detector device, and a counter unit.
A counter device is thus known in which the target is an off-center magnet fastened to the wheel, and in which the detector device comprises a magnetic relay of the reed bulb type that is mounted stationary relative to the structure. The counter unit is connected to the magnetic relay in order to detect the passage of the magnet and thus count the number of revolutions.
A counter device is also known in which the target is a piece of metal, and in which the detector device comprises a coil of a resonant circuit. The counter unit is then connected to the resonant circuit in order to detect the passage of the piece of metal and thus count the number of revolutions.
The design of such a counter device needs to comply with requirements that are very strict in terms of counting accuracy. The acceptable amount of drift that is specified for certain modern gas meters is thus typically less than or equal to one revolution for every ten thousand revolutions.
Unfortunately, the gas meter wheel and the target detector device are subjected to multiple constraints that tend to disturb counting: mechanical drift, e.g. due to vibration, to wear phenomena causing the wheel to warp, to components aging, to temperature variations, etc.
The counter unit of the counter device is also subjected to multiple constraints. The electrical components of the counter unit are in particular subjected to radiofrequency disturbances and to disturbances on the power supply.
Radiofrequency disturbances result in particular from radio waves being transmitted by the gas meter or in the environment of the gas meter in order to transmit data by wireless communication. By way of example, the transmitted data may be data concerning the quantity of gas distributed. By way of example, the wireless communication may be of the radiofrequency identification (RFD) type or of the near field communication (NFC) type.
Power supply disturbances result in particular from transient inrush currents that can occur each time the counter unit starts (since it is kept on standby for most of the time), where such an inrush current causes a drop in the power supply voltage that is of short duration, but relatively significant.
These constraints and disturbances together tend to reduce the counting accuracy.